"I love my uncle and aunt."
Translation:Я люблю своих дядю и тётю.
"my uncle and aunt" is a direct object for "I love" and is in the accusative case. You should use the appropriate form of the pronoun: the accusative of "свой" is "своих" and it matches the genitive since the direct object is animate.
The pronoun here refers to the subject of the sentence (I), hence "свой" (not "мой").
A very handy and very useful source that shows the conjugation forms of common verbs and the declension forms of common nouns and adjectives is:
nouns: https://cooljugator.com/run adjectives: https://cooljugator.com/rua Try it; you WILL like it. It has saved me much frustration. I only wish I’d found it a long time ago.
They are animate objects and need to be in accusative case. The genitive case is used to form the accusative case for animate objects (that's why also the pronoun is своих instead of свои), except for words in feminine declinations ending in -а/-я. There, the accusative is formed just like for inanimate objects. This is also valid for adjectives/possessive pronouns:
I love my aunt -> Я люблю свою тётю
I love my small dog -> Я люблю свою маленькую собаку
BUT: I love my fat uncle -> Я люблю своего толстого дядю.
Дядя, like папа and дедушка, is a male noun and needs male adjective declination but the word itself is declined like a female noun.