When a legal form refers to an immediate family member, are son- daughter-, father-, and mothers-in law considered the same as a son, daughter, father and mother?
For context, here are two situations that have long been resolved, so don’t worry about putting in the IANAL or other disclaimers.
They gave us a car. When registering/titling a car in New York, you need to pay sales tax—unless it’s a gift. How the Declaration of Gift form gets filled out depends on the relationship (i.e. immediate family v. stranger). Could I have put down myself as owner and checked the “son” box?
They own a small business. I help them out bureaucratically. In filling out a Federal IRS form to make me an authorized agent and allowed to talk to the IRS on their behalf, there is again a distinction between family and non-family members. Could I have just checked “son” and been done with it?
Those are just two tax-like questions. I assume this could also come up in real estate and contract law, but I haven’t directly come across anything. Barring a contract that directly addresses it or special circumstances, is the default interpretation that in-laws are tantamount to family members?
(Again, don’t worry about disclaimers. Both cases would have been easier to use my name, but we used Mrs. Devil to keep things simple. Since this is a question of generalized curiosity, feel free to use any jurisdiction/context you like.)
In my experience when in-laws are included the definition will specifically include them. For example, the definition may define "immediate family " to include parents, children, parents-in-law and children in law or to include the “parents, siblings and children of either you or your spouse”. I don’t think a son-in law can just check “son” and be done with it.
First, because these forms are not distinguishing between "immediate family and stranger" - they're distinguishing between immediate family and anyone who is not immediate family. A cousin is not a stranger, but neither is s/he immediate family.A son-in-law is family, but he's the spouse of an immediate family member, not one in his own right.
Second, the form is just filled out differently if it’s not a specified member- it doesn’t mean you can’t get the result. I gave my daughter’s boyfriend a vehicle as a gift and he didn’t have to pay sales tax on it. I just answered the extra questions asked when the recipient is not one of the specified relatives.
Third and probably most importantly, while no one would have a problem with the IRS or DMV just adding in-laws to the list of relationships, there are any number of areas where most people would not want the son-in-law to be the equivalent of a son. I don’t know that I would want a son-in-law making medical decisions for me as a next-of-kin or and I know I wouldn’t want my estate to be divided in three equal parts between my daughter , my son and my daughter-in-law if I die without a will.
If there is a box marked “son”, a son-in-law would NOT check it. If the box is marked “immediate family”, an in-law would NOT check it. But if it simply says “family” or “relative”, I would tend to say okay.
That said, can we discuss what the heck the term “son-in-law” actually means? I’ve always imagined it to mean, “Legally a son, even though not biologically a son”, which would allow you to check that box. I’m very confused, and the relevant Wikipedia page seems totally useless.
There’s a bit more of an explanation if you click the link to Affinity:canon law. What it seems to come down to is that under some systems of law, your spouse’s relatives are/were the equivalent of your own relatives for the purpose of marriage. So if marriage between man and his sister was prohibited, it was also prohibited for him to marry his deceased wife’s sister .
As for what it means in English now? It's mostly just a warmer way to refer to your daughter's husband. When someone actually says "my daughter's husband", it always sounds to me like they don't like the guy, at least temporarily.