1. Abuela = Nuestra. It would be Nuestra because Abuela is a feminine word and nuestra would represent a feminine word.
2. Hermano = Nuestro. It would be Nuestro because Hermano is a masculine word and nuestro would represent a masculine word.
3. Primos = Nuestros. Primos is a plural and masculine word, so you would use Nuestros because it represents a plural and masculine word. You can see this by the addition of the s.
I hope this helps!
