Here are all the possible outcomes for having 4 children, sons(S) and daughters(D):
SSSS+ DSSS+
SSSD+ DSSD*+
SSDS+ DSDS*+
SSDD*+ DSDD
SDSS+ DDSS*+
SDSD*+ DDSD
SDDS*+ DDDS
SDDD DDDD
The starred * items show which entries have exactly two daughters
The entries with + indicate cases where they have two or more sons
Hence the intersection is the 6 entries with *+