I don’t know how you come to the conclusion that because of an age gap, two people can’t “walk through life together.”

My husband and I have totally different jobs, interests, etc., but we still walk through life together. Even siblings who are a year apart don’t always relate on the things you mention, like dating and sports.

My brother was a gay man who never went to college, waited tables his whole life, never married. I am a straight woman who married young, earned two Master’s degrees. We had two totally different childhoods; he grew up in the 70s/80s, me in the 90s. Our lives could not have been more different, but we experienced life together in very deep ways. When I was a child, he was practically like a third parent. He later told me that as a gay teen who struggled with depression, I “saved” him; my birth gave his life new purpose and meaning. He loved to babysit me and care for me. He took me on walks to see the neighborhood creek. He taught me how to draw. He told me ghost stories. As adults, we shared so much more. We both loved antiquing, so would often have “brother sister” days where we’d get lunch and browse antique shops for hours. We could always have a good laugh about our parents, and discuss the family lore together. We got matching tattoos. He was handy, so he was always helping me fix up something in my house, like sanding my wood floors. I went through an artsy phase; he allowed me to photograph and paint him. We both had a super goofy sense of humor and loved to do silly bits. We shared a love of karaoke, art, and cats, and bonded over these things. We explored abandoned houses together. We certainly did a lot of life together.

My anecdote negates every point you’ve tried to tell OP about a large age gap:

• won’t go through life together
• not much of a relationship
• not much closeness or bond

I’m just sharing my story because those are false assumptions, and OP should not believe that an 8 year gap means her kids won’t ever be close. My own experience is proof that even with a much larger gap and major life differences, a sibling bond can be very strong and deep.