write a personal letter of love to each person that has made an impact on my life

I am wanting to writea letter to my Wifes gradndparents to express my love an dappreciation for them despite the fact that their granddaughter and i are seperated.(Not my choice) I realize i made mistakes and do desire to work out the problems my wife and i havehad with teh help of counseling but i alwasy loved her grandaprents. they made me feel as ifthey wer my grandparents. Their Son(My wifes Dad) passsed away in 2000. Thers’ nota day goes by that i don’t miss him and his close friendship.
the letter is really a n apology letter as well since i feel like i not only let them down an dlet down my family but i feel like i let down teh memory of their son. Please forgive me, understand i do love you and do desire to make up for all teh mistakes i made.
thants about it though i don’t knwo how to start and wind it up. a template for this sort of thing would be greaat. I don’t generally write letters anynore. but in this case, they don’t have internet and a letter is more personal than a card.