The way I'm gonna explain this is going to make me sound autistic so bear with me.

So my family and I were invited to a party by one of our friends and my brother and I were talking and I noticed these two girls talking to each other relatively close to us. My brother and I wanted to check out a painting on the other side of the room and a minute later a noticed the same two girls talking to each other relatively close to us again. Much later in the night one of my friends at the party mentioned that he thought he noticed those two girls were following us without me even mentioning it so I wasn't just making the IOIs up in my head.

So my question is how would I cold approach these two girls? Should I just introduce my self straight out with a handshake or do something else?