Hello, I am new to stata, and making use of DHS Data set, b4__01 to b4_20 are the sex for the number of children each respondent have, while b8_01 to b8_20 are the corresponding ages. how do I sort to form a new variable for the sex of children with ages 10 and below?

below is the commands i did
*to merge all the children into a single variable b4
egen b4= concat(b4_01 b4_02 b4_03 b4_04 b4_05 b4_06 b4_07 b4_08.......), punct(,)

*to merge all the child age into a single variable b8
egen b8= concat(b8_01 b8_02 b8_03 b8_04 b8_05 b8_06 b8_07 b8_08.....), punct(,)

but when i run a probit regression I get an error message of no observation.
thanks