Generating a choice list for a repeat from another repeat

1. What is the problem? Be very detailed.
I am creating a form to capture household data. In my form, I have a repeat that asks for the date of birth of each household member. Once I am done registering all the household members, a new set of repeat questions are supposed to pop up. The second repeat registers details about children aged 12-23 months in the household.
However, I would like the names and numbers of these children be populated as select_multiple list so that I can loop through the lists using a repeat and record the details about each kid one at a time.
I have done the necessary calculations to get number of kids in that category. My greatest challenge is "How do I pull those particular names of the kids aged 12-23 months and display them as a select_multiple in the next question. "
2. What app or server are you using and on what device and operating system? Include version numbers.
I am developing an XLSForm for android operating system in Smap Server. The OS version is 9.1
3. What you have you tried to fix the problem?
No clue. Since I am yet a novice
*4. What steps can we take to reproduce the problem?
Suggest a way of how I can get that list populated
5. Anything else we should know or have? If you have a test form or screenshots or logs, attach below.
hh_survey.xlsx (13.7 KB)

hello @jobdraku , welcome to the community. I haven't done this so far, but I understand I have seen similar chain of conversations earlier. I will try to find and share them with you but in the meantime also wanted to bump the conversation up to see if anyone already aware gets to respond earlier.

give me some time and I will hopefully get back to you with what I can find.