For this case, the first thing you should do is choose a verbal time.
Suppose that the verb tense is simple present.
We must conjugate the verb correctly for the third person of the plural.
We have then:
Ellos/ellas tienen
Then, the complete sentence in Spanish is:
El papá y la mamá tienen dos hijos.
The translation of the sentence in English is:
The father and the mother have two children.
Answer:
Tienen
El papá y la mamá tienen dos hijos.