Quite a number of people could join such a club (collegia) and one way to ensure that they all could be buried was to construct a columbarium (literally pigeon house).
A columbarium in Ostia (B8, seen from the south). Notice the small niches, each one designed for a ash urn.
[M(arco) Antonio Hiber]o P(ublio) Mummio Sisenna co(n)s(ulibus) Kal(endis) Ian(uariis) collegium salutare Dianae / et Antinoi constitutum [...]
The first of January, during the consulate of Marcus Biberos Hiberus and Publius Mummius Sisenna [133 A.D] was Dianas and Antonius funeral club founded[...]
ILS 7212 (inscription from Lanuvio/Lanuvium)
Translated by Patrik Klingborg