Since you want some spoiler.. At this point, there's no indication of that Yiyi nor Fengfeng know's the existence of the baby. The baby was just born and the aunt had a baby sitter taking care of it. Seems that everytime she tries to carry/hold the baby it keeps on crying lol. The english translation is just behind by 3chapters only from the raws so there's no much info yet of whatever big will happen in terms of the baby reveal.
But we can surely hope that in the future Yi Yun will have the custody for the baby as part of his happy ending.
OMG OMG AAAAA I HOPE HE GETS HIS BABY
WAIT HOLUP SOMEONE TELL ME THAT YIYI WILL GET HIS BABY FROM THE AUNT... SPOIL ME