Our two neutered mail cats are two plus years apart in age, not litter.
The 3 legged cat Kuuipo (Hawaiian for sweetheart) the
lickee is almost 4 now.
However, as you can see by the photos, they sure like each other and treat one and other as they were buddies from day one.
The younger guy Kalah (Hawaiian for son) seen here as the licker is 15 to 18 months old.