I get it when your parents are away most of the day and the only time is being at the table, haven't even had the eating part as I was cooking for myself since I was about 7yo... even during holidays we didn't share much time so there wasn't much family connection.
Hiro father marrying again and his stepmom didn't share time together either, then his brother was born and he felt even more abandoned, that's why he has issues with connecting with someone else, difficulties in conveying own feelings towards other people.
Thanks for the scanlation!