My ex’s “cousin”...

I was with my ex for 3 years. His mother has a very close friend, so much so that their kids would refer to each other as “cousins”. They obviously aren’t blood related but would it be weird if I dated one of the “cousins”?

- the relationship ended because he started a new job that took up all his time, I barely saw him anymore even though he lives like 10 minutes away. He always had an excuse to not spend time with me... unless it was for sex of course.