Translation:I am the responsible brother, although I am the smaller.
In English there should not be a defenite article before 'younger' or 'smaller'. And smaller in this sentence doesn't make sense. Technically it is a possible translation for קטן יותר, but in this context (responsibility), it shouldn't be offered as a correct translation.
Report it using the flag, more effective than posting in the comments.
I've applied to become an admin for this, since I'm finding lots of issues. Technically, although it's used in spoken Hebrew, it should be אף על פי) ש) instead of למרות ש.