from day 1 after 結婚斟茶.. my husband told me to call them 'ba and ma'...but my real ma doesnt like..and say i should call them '62 and 99' wor..cos i only have one 'ma and ba'.they r not my real parents..but still i call them 'ba and ma'..
i think u better ask ur husband once again...cos after what my mom said...i spoke to my husband...he said i dont often see my c2 or 99 so it doesnt matter...jus follow him to call 'ba and ma' is fine...
maybe u can also ask ur 99 in person whether she likes u to call her ma or 99...