I noitced that all my villagers is at least 51 years old.
At that age, female villagers cannot have babies any more.

You're in trouble; but there are events that can bring new villagers to the island. There are a lot of stories here of tribes that survived despite the worst; start a new tribe, if you like, but I wouldn't give up on them.

I got only one female villager of pop of 14 and every baby shes had is boys she is age 27 so there is still time.

Really, I had a villager at age 72 have triplets in a game, i forgot which one, vv1 vv2 or vv3, not sure. Although she had them with an 18 year old

Most likely it was VV1, Blue Mist. There was no age restriction in VV1, but in VV2 and VV3 there is an age restriction.