Answer:
I think it would be Nunu or Mary.
Step-by-step explanation:
So, just so I'm getting this correct,
There is a 'father' figure. This father figure has a daughter, presumably named Mary, who has five children, all with these names (in order)
nana
nini
nono
nene
The obvious pattern are vowels (a,e,i,o,u) so the next name would most likely be Nunu.
But I feel like this question was typed wrong;
The question is presumably:
"Mary's Father has five children; the first one is nana the second nini..."
nana
nini
nono
nene
If Mary's Father had these children, then they would be the siblings of Mary.
Therefore the fifth child's name would be Mary.