Having a popular name, Thomas FORREST's life is hard to confidently report.
He did attend school at 5, but only stayed a few days having contracted measles. It's not clear that he ever returned.
It's possible Thomas married, but there are several candidate marriages, the majority of which relate to other Thomas FORRESTs who can be found in the 1939 Register and who have the wrong birth year.
One potential wife, Nora YATES, is in the 1939 Register aged 36, married/widowed (the enumerator's entry appears to be corrected from M to W or vice versa) and living in Darwen with her aunt(?), Margaret YATES, her son(?) William G FORREST and her brother(?) a serving soldier.
It is possible Thomas died young: a 28 year old Thomas FORREST died in Q3 1934 in Blackburn would fit with Nora and William G.
Major problem is that Thomas would only have been 17 (almost 18) when he married, but there were no early children to necessitate an early marriage. William G wasn't born until 8 years later in 1931.