I can't hire a crew member?

So, I really like to have a multi-racial set of crew (I think that is accurate?). Since I have limited space currently, only enough for 4 crew, I fired my extra Hylotl to try and get an Avian that was available. For some reason he talked about wanted to go on the ship but it wouldn't work.
I am 100% sure there is an extra spot. And I didn't have two crew members following me (because for some reason that messes recruiting up). So I'm not sure what's wrong. I kinda quit on that one to hire a fellow Floran but she refused also. (BTW how can a plant be female?)

 

Plants have sex, y'know

Ya sure they were wearing a protectorate uniform?

 

Yes they were indeed wearing the uniform. I don't think any NPCs actually talk about wanting to go into space for the most part without wanting to be a crew member. I do wish that the people who wanted to be crew would stand a bit farther from everyone else in a massive town because it can sometimes be hard to click on them, often I either click on a door, my crew members, or random people
Side question, what is the point of clicking on crew members to make them stay? All I can think of is to make them guards in a town of yours, but I tend to like bringing them with me instead.

 

Try using the Custom NPC+ mod?

 

Female plant: Pistil, collects pollen to produce seeds.
Male plant: Stamen, creates pollen.
Sort of like animal reproduction.