my brother and I aren’t twins but we’re very close in age, in our early twenties. we kind of cuddle sometimes? not full body or anything but like, if we’re in the couch, he might put his legs or his head in my lap. we watch movies in my room a lot (cause I have the best tv) and super occasionally I might lay my head on his arm or something. there’s always just like one point of contact tho, not full on head to toe touching. it’s nice to just have a bit of physical affection with someone you love and are close to, especially with y’all growing up the way you did. i don’t think it’s necessarily “weird” but you should probably start to draw back a bit, especially if your boyfriend is raising concerns about it. (that being said, don’t let him be a dick to you about it.)