Thomas and Jasper were in the same year at Hogwarts, albeit different houses. Thomas was the loud, boisterous extrovert that would more than likely either have pranked Jasper multiple times or tried to befriend him and get him to open up because he's just annoying like that. Thankfully, Thomas left after his OWLS xD As a former classmate, he may have sent him a condolence card after hearing about his brother.