I don’t want to raise here the question of Mary’s virginity, but there are some aspects of Joseph marriage that the catholic preachers surely wondered about but were afraid to tackle in their sermons.
How long was Jesus born after his parents marriage ? Nine months ? Cunning question. 
Nine years ? Did they sleep in chambre séparée ? (until Jesus’ birth and forever thereafter). Hard to believe since Jesus was born in a stable. Poor Jo, what a life! Perhaps was he impotent ?
Why did he get married in the first place ?
Joseph found out that Mary was pregnent before their marriage, so Mary was probably at least a few months pregnant at the time. I suspect that most people who knew them assumed that Joseph, um, jumped the gun a bit 
The Catholic Church believes that Mary remained a virgin for her entire life, but as a devout Catholic myself, I’ll be the first to admit that they’re on really shaky ground with this point. Nothing in the Bible indicates that Mary and Joseph didn’t have sex after Jesus’ birth.
According to the Bible, he got married because an angel told him to. To say much beyond this would take us out of the factual realm of GQ and into IMHO or GD territory.
Note, though, that Catholic teaching is that Mary remained a virgin throughout her life, while standard Portestant belief is that Mary and Joseph had normal marital relations after Jesus. Here’s a relevant Straight Dope column.
Why does anybody get married? Just because your intended is knockin’ boots with God Almighty (and wouldn’t that give you an inferiority complex about your equipment) dosen’t mean you don’t get hitched for all the reasons you were going to do it anyway.
Seriously, they did have other children, scripturally.
Church tradition relates that he was an old man at the time of the marriage, having already had previous marriages and several children already. He was taking Mary on as a wife primarily to be a caretaker for her; she was committed to virginity already, and Joseph never had any intention of consummating the marriage.
The Eastern traditions teach that the siblings of Christ mentioned in the Bible (including James the brother of the Lord) were actually half-siblings, being children of Joseph from one of his previous wives.
Wouldn’t that make them step-siblings rather than half-siblings?
Er, yes, now that I think of it. Half-siblings legally, as Joseph was legally Christ’s father; step-siblings biologically, as Christ received His humanity from Mary only.
Actually, it might not have even been jumping the gun.
According to Jewish law, marriage is done in two stages: the first is called kiddushin (betrothal) and the second is nisuin (marriage).
Betrothal is really a poor word to use for kiddushin because it is much more than a mere betrothal. Kiddushin renders a woman forbidden to all other men. If she wants out of the marriage (or if he does) a full divorce is required. However, the husband is not allowed to live together with the bride until after nisuin.
Today, both stages of the marriage are done together. However, in Biblical and Talmudic times, there would be a gap of up to one year between the two. This was fairly common back then.
There are three legal ways to effect kiddushin: (1) The groom can hand his bride money or goods worth money (today a ring is used universally), (2) he can hand over a document stating that she is betrothed to him or (3) he can cohabitate with her for the purpose of kiddushin. Today #2 and #3 are not used (sorry, guys).
If one wants to discount the possibility of a virgin birth, one could easily say that Joseph cohabitated with Mary for the purpose of kiddushin (making her betrothed) and that cohabitation could have resulted in a pregnancy which was, for all intents and purposes, legal.
Zev Steinhardt
I find this interesting, simply because the idea of “celibate marriages” is completely foreign to Judaism. From whence does this tradition draw?
Zev Steinhardt
Mainly from the Protoevangelium of James. The tradition is that Joseph and Mary were betrothed, and after that they lived together, but didn’t live together, if you know what I mean. She lived as a member of his household, but not as his mate.
In modern Judaism, if a man and a women are betrothed, but never consummate the marriage, does that have any effect other than the obvious (i.e. that they remain betrothed and nothing else)?
Well, as I mentioned earlier, both parts of the ceremony are now done together, so a woman is technically only in a betrothed state for no more than 15-20 minutes.
If, however, one were to perform kiddushin and never go forward with nisuin then she remains forbidden to marry anyone else, as does he.
However, I don’t know why anyone would do this. Celibacy is not a virtue in Judaism - indeed, it is frowned upon. A woman has the right to ask for a divorce if her husband is not intimate with her enough. Furthermore, any engagement that is entered into has to be one that is capable of being consumated. As such, if a person were to perform kiddushin with his sister, for example, the act would be meaningless; since co-habitation is one of the primary purposes of marriage. That being said, the whole concept of a celibate marriage (as proposed for Joseph/Mary) sounds strange to me, as, I suspect, it would have to the vast majority of Jews who lived in Joseph’s day.
Zev Steinhardt
I was just about to ask about the very same matter. I have suspected as much for the last several years, but I have never gotten around to asking a Jewish source, preferrably one steeped in history.
I don’t suppose that a smallish group of Jews, a sect or a group with a special devotion might have a different take on matters and go for such marriages-of-protection (as an option)?
I’m not asking for a broad, hypothetical answer. To that one might very well answer that no one could be absolutely sure not, depending especially on how small is small. I’m asking wheher we can in fact rule out any positive historical example existing for such a group.
And just offhand, (without any source on NT apocrypha handy) I’m thinking that the Protevangelium of James was written rather late, long after the “facts” it refers to. Late, and probably to a group to Christians who, even if they included some with Jewish ancestry, had lost touch with Jewish customs and history and so did not fall down to the floor laughing. Probably “James” himself did not know how strange his narrative would sound to Jewish (or more Jewish-savvy) ears.
Am I correct in this?
True Blue Jack
Actually, it was written sometime in the middle of the 100s. It is not a late document, and almost certainly based on an earlier oral tradition.
Quoth zev_steinhardt:
I’m having difficulty reconciling these two statements. Does this mean that the couple are allowed to have sex before any ceremony, but until the nisuin, it always has to be “my place or your place”? Or is the first sex act (the one which initiates the kiddushin) allowed, but subsequent acts have to wait until after the nisuin ceremony?
Your latter assumption is correct.
Zev Steinhardt
But that wouldn’t make any sense. Joseph was going to divorce Mary when he found out she was pregnent, so it looks like he’s certain that the baby isn’t his. It took a visitation from the angel Gabriel to convince him that everything was still OK, and that his wife-to-be wasn’t a tramp who was cheating on him. It certainly looks like he didn’t take option #3.
Then again, I don’t have any problem accepting miracles, so I don’t feel any pressing need to concoct an alternate explanation.
BTW, I don’t really care if Mary and Joseph had other kids later; it’s always seemed to me like the concept of Perpetual Virginity arose from the idea that sex was inherently sinful, and that Mary would become impure if she ever lost her virginity, even if it was with her husband and it was fully proper and nisuinized and everything. Basically, I think that the Church is being a bit prudish here.
And thanks for pointing out the difference between kiddushin and nisuin. I’ve always wondered if being engaged was more binding back then.
I wonder what the exact timeline of the Joseph thing was.
As soon as the angel showed up to tell Mary the news, she split and went to hang out at her cousin Elizabeth’s house for about 3 months. She probably came home right after John the Baptist was born.
I’m wondering if Mary broke the news to Joe before she left, or if she waited until she was 3 months gone, after she came home.