We just see certain things happen before other things, and remember having seen such before- and - after sequences at earlier times.
라는 문장에서요 동명사는 시제를 반영하고
본동사보다 시제가앞설때 having pp 쓰잖아요
근데 의미상 remember동사는 과거에했던일을 나타낼때 ing를 쓰는데 having pp랑 차이가뭐죠

그리고
How I wish I could tell her that even twentysix years later, her kindness has never been forgotten.
이라는문장에서 I wish가 삽입이 된건가요?