Does he have any ideas? It’s hard to tell from those photos. Virginia creeper is quite similar, but it comes in clumps of five. It seems like your photo has clumps of three, but it’s a little hard to tell. That said, it doesn’t look like clumps of five, either.
Here’s a link to look-alikes. See if any look similar to you.
No, not virginia creeper. I have experience as a landscape designer and am familiar with most of the plant materials on the market in the midwest. As far as my knowledge suggests, this is a native not a cultivar.
Not sure what it could be, but there’s one way to tell (or at least tell if it’s similar enough to poison ivy not to matter).
Step 1: Buy some calamine lotion
Step 2: Have your sister’s boyfriend handle the plant if he’s so sure.
Step 3: Hand over lotion if necessary.
Or for extra fun, skip steps 1 and 3.
He seems to be jealous of my sister’s time; when I make dinner he takes the boys out to eat. Etc. Very passive aggressive. So it’s possible he’s only saying it’s not PI because I said it was. To demonstrate his intelligence: He said he knows it’s not PI because he rubbed it on his arm. Then he said PI doesn’t affect him, but still he could tell.
I think you need a new sister’s boyfriend. This one sounds like a loon.
It depends on how carefully maintained your suburbs are. 
Poison ivy leaf margins are pretty variable, but I’d say that is DEFINITELY poison ivy.
Poison ivy, oak, or sumac. Either way, I’d go with what the Boy Scouts taught me: “Leaflets three, let it be.”
Not in the East? Poison Ivy grows all over the mid-west and New England. Typical places? I’ve seen it growing in cracks of busy sidewalks. “typically” leaves are shiny, unless they are not.
I know I’m late, but I’ve been on vacation. Yes, that is poison ivy! The woods surrounding our house are full of it. When we moved in several years ago I had an expert confirm because I wasn’t sure. (And my husband has gotten it several times from doing yard work.) You can get a product called ivy block that you can apply to your skin for extra protection against it. Be sure to wear gloves and throw them away when your done. And be careful with your clothing - if it brushes up against the poison ivy, the oil will transfer to the fabric and be able to cause a rash for quite some time, so be sure to launder it right away in hot water after you are done.
If your sister’s boyfriend doesn’t know what it is, then he doesn’t know that it’s not poison ivy. Maybe he was stupid enough to do a rub test, but that wouldn’t prove anything if he’s not sensitive. More likely, he’s just an idiot who doesn’t want to admit that he’s an idiot.
Yeah, poison ivy in the east, poison oak in the west. Two different species in the same genus, which are essentially identical in terms of their effects. And you are better off avoiding something with “leaves of three” that isn’t actually some type of Toxicodendron than deciding something isn’t Toxicodendron when it is.
And you can develop sensitivity to the stuff even when you didn’t have it before. When I was younger I used to be able to wade around in it with impunity, apparently, and didn’t pay much attention to identifying it. People I was with would get it and I wouldn’t. A few really nasty cases when I got older sharpened my ability to recognize it.
I hike the SF Bay Area / Santa Cruz Mts a lot, where poison oak grows profusely, and I use Tecnu whether I think I’ve gotten into some of it or not:
http://www.teclabsinc.com/products/poison-oak-ivy/tecnu
I think it does help. I also have an unsubstantiated opinion that the sunscreen you put on primarily to prevent getting sunburnt also helps a bit for poison oak by providing a physical barrier against minor contact.
BTW, THIS year seems particularly bad for poison oak. At this time, it’s easy to identify because the leaves have turned red, and it is just EVERYWHERE. Must be drought tolerant, dammit.
This is Poison Ivy.
Funny, that doesn’t look like her.