Even after you've beaten the main quest/story, the gallery unlock "feature" doesn't work... oh joy.
From what I have heard the problem is that the gallery was a mod someone made for an earlier version of the game but was later included into the game by the creator. However the gallery was poorly implemented and the unlock all feature was actually locked, so while it's there it's actually from when it was a mod and is unusable at the moment. It also crashes the game quite frequently, especially if you try to view the female PC scenes.
1last question can the mom be pregnant
No she can't.
There are only a few that can be impregnated and it is only during specific scenes.
Pregnancy
Male PC
Meredith - After having 17+AP in act 2 after doing a scene in the castle bedroom just go talk to her to get a scene to impregnate her.
Ruksana - To impregnate Ruksana you have to during the sex scene in the interrogation room pick the whip + have your way with her and then choose vaginal sex to impregnate her.
Tiah - After the rescuing Jerrah just ask for sex.
Clawyn - After having 15+AP and having done the 69 scene in the castle forest she will meet you in the bedroom and ask to start a family accept and you will have a sex scene to impregnate her.
Jenda - After finishing the Emek's Rest side quest you get the reward of impregnating Jenda, while the game guide say's you impregnate both daughter and mother, Jenda + Jerrah you can only pick to have anal sex with Jerrah so don't think she actually get's pregnant. There also isn't anything that happens after this like changed dialogues so it's hard to tell.
Abby - Just do the sex scene by asking if she has someone special.
Flowers of Geli - During the main quest in act 2 after rescuing them you can choose to impregnate them, if you choose to do so they will appear again in act 3 and there will be an extra sex scene.
Tevararae - After doing the main quest in Ornesse during act 1 you can go and accept a quest to rescue Tevararae's daughter if you do, you are given the option to leave your "legacy" with her.
There are also a few others I believe where it is semi-implied that you might have impregnated them like, but for the most part like with Teva and Jenda you won't actually get any follow ups to actually know if you impregnated them or not.
Edit: just unlocked the new seer scene and it seems you impregnate her and she leaves because of becoming pregnant.
Female PC
There are actually a lot of times the female PC can become pregnant but their mostly chance based like having sex with human males might have a 20% chance to becoming pregnant and so on.