Hi there!
The correct answer is:
"Mis tíos no eran muy ricos, pero en su casa siempre había helado para nosotros." (ser/haber)
Ser and haber verbs are in past imperfect tense. In the first blank with corresponds to "eran" of "ser" needs to be in plural past imperfect because you are referring to "mis tíos" which in English stands for my aunt and uncle. The second blank which corresponds to "había" of "haber" needs to be in singular because it refers to "helado" which in English stands for ice-cream.
