Humans are CREATED (?) as social beings. Interactions between them is unconsciously encoded into their psyche !
This account for "LONELINESS " when that link of socialisation is severed by whatever . That situation is akin to loosing an important organ in the human system. It must manifest symptom of ill health .

Loneliness is absence of the social link of interactions between species .

But it should be noted that socialisation is not and can't be universal. What is considered as socially "good " in some climes is regarded as a misnormer in others because of the subjective nature of what we call IDEALS.

Thus what one deemed " inappropriate relationship" is another's appropriate relationship. Mutual acceptance is therefore what distinguishes one from the other , despite some undemocratic imposition of some by governments and traditional authorities !!