Not sure about it. Also depends on the age. If someone had 3 exes at the age of 35 I wouldn't be concerned at all, but having had 3 exes at the age of 16 might be weird.
My ex had like 3 or 4 bfs before me, got together with another boy 1 month after, they broke up and now she's got another guy for 2 years. She's now with her 6th or 7th boyfriend at the age of 22 - which is a lot to me.
I'm still somehow bound to her and she was the one who really got me into the Netherlands, funny thing I might study near her but I'll never see her.

Things turn out to be crazy sometimes I guess.
Sometimes I'm really sad about the fact I Iost my virginity to her, but it was me who left her, so that's nothing I should worry about.
I'd also be concerned if someone never had a relationship when they hit 25. Kinda sus