Are goyim metzuvah in the mitzvah of peru urevu?
It is controversial if gentiles are commanded in the mitzvah of pru urvu. Although they were certainly commanded to do so at the time of Adam and Noach, however the question remains if they are commanded so even after matan torah. The Gemora in Sanhedrin 59b seems to say that it does ot apply after matan torah, (see tosefos there), Also see Shulchan aruch Even Haezer 1-7. However see Sha’iltos 165 and the commentary of Heek Davar, and Rashi Yevamos 62a.
Aside for the actual mitzvah, there are other ramifications and questions about this. For example, if there is a prohibition for a gentile to lose seed, see Sefer Toldos Noach chap. 4-36, Pg. 272-276.