How do you say your uncle like to read and he is atletic?
When you say "your" you don't state if you are on a first-name basis with that person to whom you are speaking (tú) or formal (Ud.)
familiar = a tu tío le gusta leer y es atlético.
formal = a su tío le gusta leer y es atlético
OR perhaps you mean "MY uncle, etc." = A mi tío le gusta leer y es atlético.
Sra