Manslaughter, voluntary or involuntary is a crime against moral turpitude. You being young and have never met him and are talking about marriage is sketchy. We see a lot of felons in the USA looking for an easy way out and you may be a victim of such. Just like some people mentioned here, there is more ahead than just trying to get here and work and live. Being a felon in the USA is challenging and you must be ready mentally to support him. Study him, don't hurry into something which you know you will be the one spending in almost everything, we see a lot of such cases here everyday, talk to family and friends, open up before you venture into this, no parent will want to hear about this kind of adventure when it must have taken a sad turn already. I am not judging you, just being straight forward here.