It's a great capsule, Kate, easy to read and insightful. The big thing you missed:
Cross species kids actually do happen. Mr. Spock from the original series was half human, half vulcan.
In The Next Generation, Mr. Worf: a klingon raised by humans, had a love interest who was half kingon, half human, and they had a basically Klingon child, Alexander.
Another Half Human, Half Klingon shows up in Voyager: Be'elana Tores.
A Klingon planet occupied by Romulans was cut off from the Romulan empire for a generation or two, and a whole generation of hybrids resulted. There's also at least one Cardasian/Bajoran hybrid resulting of from the Cardasian occupation of Bajor.
That's probably a bit much information for a capsule introduction. It does seem relatively easy to for hybrid children to happen, and be fertile themselves.
That said, contraception in Star Trek is a monthly shot. It's 100% effective if both parties have it, less so if only one.
Genevieve, welcome to Elliquiy. New games are cropping up all the time, a lot of them free form and based on a fandom. If you'd like to apply to this one, Red Eve hasn't cut off the applications yet. : ) She does have a big list of those she's received (accepted?) back a page or so.
Aribeth, the only medical character we have is Brandon's genius. I don't know how someone who was a doctor at 16 managed to join the fleet as a medical technician instead of a doctor, but we don't have a chief medical officer.