Not compatible?

Y
I don't know if this will make sense to you but here it goes. I was wondering if a couples genes are just not compatible to have a baby. My husband and I have been married for 10 yrs and basically been up for getting pregnant since day one. We didn't really try until maybe 5 yrs ago and have been trying with meds... This is our second time trying first time was 4 months two yrs ago and this time I found out I have PCOS. Anyway a cousin, tried to have a baby and went to infertility Drs and for yrs she couldn't get pregnant with her ex husband now. She divorced and started dating another person and got pregnant right away. I was wondering if many it just won't happen with certain people because you're not compatible. I really hope it's not my case but I can't stop thinking that.