Perhaps another reason Taro had been anxious for Mebius, was the fact the young Ultran resembled him a lot... when he used to be of that age. Right now, Mebius had been the youngest of them brothers just like he used to be in the past. For Mother and Father to worry about Mebius, it was not something to be surprised about. Mother used to worry about him too. But for him, his reasons to worry was much more than that. Because he still remembered how being the youngest had influenced him.
He used to remember being too dependable on his four older brothers. How he used to think that regardless the situation, his brothers would be around to help him. He used to receive a lot of scolding from Ultraman, Seven, Jack and Ace about that.
That was why, when he was given the task of training Mebius... he decided early on to teach him this particular lesson. This time... Ultraman, Seven, Jack and Ace were not around to help them in case something bad happened; in fact, none of them knew what happened to them since twenty years ago. Even if there were other of their fellow brothers—including him—who could help Mebius in times of need, there was no guarantee that those help would arrive in time. So Mebius should learn to be able to fight on his own without having to rely too much on the help of his elders.
But perhaps he had taught him too well... or perhaps, he should not have let him listen to his older brothers past feats too often. Mebius had stubbornly insisted to continue fighting alongside him despite his injuries. So much the same spirit as his brothers and himself also had. If Mebius was like any other Space Garisson Ultramen who had fought for Earth before, he would have had more faith in him. But Mebius was still a rookie, there was still a lot for him to learn. There was a limit to what you can force yourself to do...
Then again, perhaps all these years had made him forget. In the past, despite his own flaws and weakness... he too had learned to be strong on his own. It took a bit of time though, for him to learn it... but he did. The same should apply to Mebius.And learn he did, Mebius has started to become stronger. Guess for now, they need to have a bit more faith on this child of the family. After all, Mebius have Crew GUYS by his side.