In his youth, he was often in the shadow of his extraordinarily talented older brother Albus. He later described himself as having been raised surrounded by lies and secrets, which may indicate that he did not have a happy childhood.Also ,Aberforth blamed Albus about Ariana's death ever since, actually breaking his nose during her funeral, and resented him for it for years.So Aberforth was jealous on his elder brother , and on the funeral of Albus he never showed any outward sadness because he conformed with Albus' death and he wasn't the type of man who was very touchy. He was most likely emotionally sad. On the inside. He could even have been jealous for Albus would be with Ariana again.