There are people you grew up with who for no other reason than their genetically designed brain-chemistry cannot conform to your particular perception of what is supposed to be happiness.
Your mood might shift between peacefulness and frustration depending on mitigating or aggravating external circumstances, but your overall mood scale still falls within a larger scale determined by your brain chemistry, such as dopamine, adrenaline and a host of other hormones produced in your body.
Your body generally produces more of some hormones than others, then external stimulus can trigger an additional surge of certain hormones as needed for such responses as the fight or flight response, mating, nutrition-seeking (hunger or cravings), etc.
When like-minded people come together in friendship it would seem logical that the similarity of their perceptions afford them the illusion that they make each-other happy. As people grow and change with age, sometimes their brain chemistry may also change. This divergence of perceptions often happens between married couples and childhood friends as they grow older. Relationships sour often for no real reason other than the shifting balance of brain chemistry.
The relationships between families with one or more natural born children and adopted children can be especially problematic if they do not understand that the adopted child will develop with age a different balance of brain chemistry that may result in slightly different behavior and misunderstandings, like a puzzle piece that doesn't quite fit.
This is why people need to continue to try and make new friends even in old age. Some people become bitter about their old relationships dissolving, estranged family relationships; and are very hesitant to make new friends because they were misled to believe that it was their fault or their friends fault for the end of the relationships, when really there is no one at fault but basic genetic development.
Try to understand that people are not like you. They don't develop like you. Their bodies don't react to food or exercise the same way your body does. The same things that make you happy may not work for them. They do not have the same metabolism that you do. Please bear this in mind especially if you adopted a child or you have an adopted sibling.