I can see most of the questions have been answered. I would like to stop hearing whether a Space Marine can have kids or sex. IT IS NO!!! Everywhere GW and it's writers reference the making of a SM they mention they are hypnoindoctrinated (my spelling is atrocious) to the point they do not have the petty wants and needs of their once human lives. Things like wealth, power and jealousy are drilled out of them both mentally and physically. A SM only wants to do their best for their Brothers, Chapter, Primarch and the God Emperor himself. Let's face it if they wanted to make more Space Marines than wouldn't they just tap into the sperm of a legendary Brother and use it to make more SM's? The resulting kids would still need the requisite organs but would be more suited to becoming SM's. But instead Chapters "recruit" from their home world/s and of those that are recruited only maybe a handful can be transformed into a SM.
If you really need to have images of Space Marines having sex (I guess all the free porn on the interwebs is just not enough anymore) then you have to go Chaos. Their needs and wants are very much the petty human kind. Power, wealth and jealousy are all a part of them thanks to being corrupted. I would especially believe this in a follower of Slaanesh. You could maybe work in a Space Marine that slowly gets corrupted by some contact with a Warp object of some kind. In which maybe the SM starts to get thoughts and feelings he is not so sure what they are at first. Eventually he has fallen to the Powers of the Warp, but even then he would only want power, wealth and fame.