God may not have blessed you with an abundant childhood, your parents may not have always been the role models you would have liked them to be, they may not have always been able to express their love for you in words or in deeds that we associate with love - but they are, regardless of their shortcomings, your parents. For that alone, they deserve the honor and respect God commands us to afford them.
Recognizing a few of my errors in raising children, I apologized to each of them in their early 20’s. Now, they have doubled those ages and each has raised children of their own. I’ve never asked if they’ve apologized. My Beloved Husband had multiple sets of parents, birth, step and adoptive, while I had one mother, one father and thought that was quite a good fit. His birth mother let he and his brother go to their father, yet abandoned four more children by running away with a married man. My parents stayed married to each other till death did part them. They raised my sister and I actively involved in their church. Yet my mother had difficulty expressing her love, and mentioned that to my Second Daughter as a regret late in her life.
I have known people whose children might have very good cause to doubt their parent’s love, but they are not exempt from God’s commandment.
Honour thy father and thy mother: that thy days may be long upon the land which the LORD thy God giveth thee. (Exodus 20:12 KJV)
Honour thy father and mother; (which is the first commandment with promise;) (Ephesians 6:2 KJV)
Jesus spoke of this commandment in Matthew 15:3-7, ending with a description that is too often found as we speak, but do not live, His commandments.
This people draweth nigh unto me with their mouth, and honoureth me with their lips; but their heart is far from me. (Matthew 15:8 KJV)
There is no “Honour thy father and thy mother expect when they are (insert description that fits: drunk, high, verbally abusive, physically abuse, absent, divorced – the list continues).”
Nope, just as a combination of DNA identifies you as their child, they are your parents and always will be. The important thing is that we do not carry the negative emotions they generate within us. For that, we must do the forgiving, and the honoring. Jesus spoke to this on a broad scale:
For if ye forgive men their trespasses, your heavenly Father will also forgive you: But if ye forgive not men their trespasses, neither will your Father forgive your trespasses. (Matthew 6:14-15 KJV)