The Sand Princess (2019)

In both dramas the femal lead gets paid to take care of the male lead's child who was abandoned by their mother.

The basic plot appears the same. A womaniser ML has the FL as the maid and a child shows up from a previous relationship.

1. Fake marriage 2. A kid is involved (the 2nd ML'S kid) 3. The FL is tasked to take care of the kid

+ both are adopt their nephew became their kids + female lead is a nanny, even tho SP was mistaken as the mom's child + leads are started to develop feeling after taking care of the child together