Should i use separate robots.txt file for each subdomain on a root domain?

[seenalal]

my root domain in www.dontworry.com. I have a multiple of subdomains. Among them 2 are

(1) https://dontworry.com/realestate/ and (2) https://classified.dontworry.com/

so should i add robots.txt file for each of them???
i have domains which are in form as (1) i written above.

so what should i do?? please help

[soniya_ss]

First of all, dontworry. com/realestate/ is really called a subdomain? 

[soniya_ss]

seems like you are on a vacation!  #OP

[John - Smith]

It is okay if you include the sitemap links of subdomains in the robots.txt of the root file. as it is the root domain if the main robots.txt file will be crawled by crawlers, rest will be also done automatically!