Avatar purush when they take birth, they bring their supplementary ecosystem also. In Ramayana, brother Laxmana is shown suspicious or apprehensive of schemy step mother Kaikeyi & her son Bharat. Eldest brother Lord Rama always overrides such fears and being devoted brother, Laxmana obeyed it, but always nursed grouse if he had been elder brother, he would have done this and avoided that....etc..
To that statement, Lord Rama said that opportunity would be coming in next avatar rebirth i.e. Lord Krishna' elder brother Balarama.
In both cases, he had to either take orders from elder brother who had better understanding of the nature laws and rules, while in subsequent role, Lord Krishna displayed superior logic and compliance to the eternal destiny, so Balarama had no choice but to accept it.
So to say Balarama is an avatar (smaller / lesser), is ok, to the extent of his relation with Lord Krishna
In contrast, Balarama (Mahabharata) had more of family life, which he voluntarily forgone to serve his elder brother during the exile (Ramayana)