His name is Sundara, but the zoo is calling him "Sunny D" for short.
Lilly, whose last name was not provided, was born with Hypoplastic Left Heart Syndrome.
Reservations are no longer required for members.
Zoo officials say the new lemurs join Ivan and Faust, both 28, who have called Louisville's Zoo home since 1994.
Zoo officials want everyone to join in on Fitz's special day during a Facebook live at 11 a.m. Sunday.
The general public can book zoo visits for Saturday through July 31.
"Shipwreck: Realm of the Eels" will showcase the ruins of a ship now home to eels, fish and hundreds of other animals.
The lawsuit is the latest challenge for Wildlife in Need, which inspectors say has a history of animal abuse.
The zoo announced the "Fitz Weatherproof Plan" to ensure everyone has the opportunity to see the calf during winter break.
The pumpkin smash event is used for enrichment, the zoo said, and promotes the animals' expression of natural behavior.