Baby to third cousin

So i had already posted about the situation. And him being in a relationship and having two sons and not knowing of my pregnancy etc. But this question is on the genetics. I have read threw and threw and done so much research etc on risks and thankfully there is none anymore than there would be for those not at all related. However..... when my mum had initially found out i was seeing this man she was extremely concerned of me getting pregnant because on his mums end of the family there is alot of genetic problems. So i was wondering could that become more of a risk then. His two boys are fine. But with me carrying a bit of blood line could it highlight it more. I dont want to embarrass myself by getting into this with my doctor and i cant ask my mum what its called again as she will become suspicious (she isnt aware of my pregnancy yet) but i know in his family they have a disease of some sort which creates humps on there back in adult life. And they end up in wheelchairs. I know his grandmother had ms aswell. I think the diease begins with A