What is the word for something that you have to do (mainly because someone is expecting you to do), even though you don't want to do it, but you still do it. In other words, doing something that you are not interested in doing.
Example: Jenny hates babysitting her niece, but she has to do it for the sake of her sister and the love she has for her niece.
Perhaps you are thinking of an "obligation."
See the definition at dictionary.com (link direct to word entry).
1) something by which a person is bound or obliged to do certain things, and which arises out of a sense of duty or results from custom, law, etc.
Housework that must be done is usually called a chore, whether it is done in the house or not.
chore noun
A job or piece of work that is often boring or unpleasant but needs to be done regularly
I think the words burden and onus might be what you're looking for. In particular, they both have the sense of a responsibility which is unwanted.
burden: that which is borne with difficulty; obligation; onus
onus: a difficult or disagreeable obligation, task, burden, etc.
I would call that a duty.
Duty doesn't necessarily carry the connotation of something you don't want to do, but it isn't usually used to describe something that you're excited about doing, but rather something that you need to do due to an external impetus.
From Merriam-Webster:
2 a: obligatory tasks, conduct, service, or functions that arise from one's position (as in life or in a group)
3 a: a moral or legal obligation
Imposition.
- the laying on of something as a burden or obligation.
- something imposed, as a burden or duty.
- the act of imposing by or as if by authority.
Random House Kernerman Webster's College Dictionary
Jenny hates babysitting her niece, but she has to go through the motions the sake of her sister and the love she has for her niece.
go through the motions — to do something because you are expected to do it and not because you want to (often in continuous tenses) These days when we go out, cook a meal together or even make love, I get the feeling that he's just going through the motions.
— Cambridge Idioms Dictionary, 2nd ed.
Another common one would be responsibility
responsibility - noun
Something that it is your job or duty to deal with
To do something begrudgingly is to give or expend with reluctance or resentment.
You can also begrudge a task, that is to be reluctant or resentful about it.
Necessary Evil perhaps?
Something you dislike doing but just has to be done.
For Jenny, babysitting her niece is a necessary evil. She really dislikes doing it but she has to for the sake of her sister and the love she has for her niece.
In one word, "duty", as mentioned already in another answer, but there is an expression that perfectly fits your scenario, it is imported from French but used this way (in French) in English:
Noblesse oblige is a French phrase literally meaning "nobility obliges". It denotes the concept that nobility extends beyond mere entitlements and requires the person who holds such status to fulfill social responsibilities, particularly in leadership roles.
In common practice, and the phrase exists in Spanish as well, it means that you do something out of noble duty (without bitterness) as a result of your elevated status (in your provided example, the status being "loving aunt/sister").
You may use forced.
She isn't really interested in doing it but is forced to do it for her sister and the love she has for her niece.
However, I think it depends on the situation. As you're talking about babysitting here, you may use a more passive word, unlike forced. I'd prefer obliged as mentioned in the other answer.
No Catlicks on this site? It's called penance, my friends.
(Please note: It's possible that only Catholics use this word for the purpose described in the question. - we're conditioned that way.)
