Minor change in the translation. The first part, had to include the "onii-chan" thing. It might have been like how younger girls call older men "onii-chan" regardless of relation, but since this artist does several things involving playing with family (or in-laws), I'm willing to bet on it being her actual brother. She does mention she's done this before (seemingly when she was smaller).
The second part, I altered to preserve her cutesy way of speaking, and to clarify the meaning of her sentence.
It's been a while since I played with you like this, Brother~
It seems a bit painful, but since Miyo's not too heavy, you'll be fine!