FWIW: Here are some of the rules I follow when deciding whether or not to include someone in my family tree. This is just off the top of my head. If I've missed someone or inadvertently implied that I don't consider someone family, please let me know so I can fix it.
1) Publicly post only deceased relatives.
2) When sharing with others, share deceased and any living up to first cousins.
3) Include biological, adopted, foster, etc. relatives and their immediate in-laws: parents, siblings, siblings' spouses. Some exceptions when assisting close cousins with their genealogy. Including generations of relatives for every in-law is just too many people to keep track of. [If I were requested to add a family tree, I probably would because I love my in-laws! 8-) ]
For recently deceased:
4) Don't include all marriages. Include those that yielded children, the last marriage, marriages mentioned in important sources, like obituaries, etc. This is not hard set. I tend to ignore it more with ancient relatives, but with relatives recently deceased, I'd rather not advertise someone's difficulty staying married by listing seven spouses.
5) Don't publicly post information concerning mental health, including death by suicide.
6) Where many variations in spelling exist for old families (prior to about 1900?), adopt an American spelling and an immigrant spelling. For instance Cussen (native Irish ancestors) and Cushing (descendants in the US), or Donley (native Irish ancestors) and Donnelly (descendants in the US).
7) Record a source for all information.
8) Publicly, post only basic information: birth, marriage, death. This is to encourage serious genealogists to contact me for additional information (sources, burial, places of residence, etc.) which I am happy to share (within privacy constraints) and to share information that they may have about the family in question that I do not have.
9) Include individuals ...
Tier 1: for whom primary sources exist (birth, marriage, death certificates, land records, wills, ...)
Tier 2: from living family members closely enough related to know from personal knowledge and family interviews; corroboration with primary sources preferred
Tier 3: some secondary sources, such as census records, obituaries, grave markers, biographies, town histories, etc.
Tier 4: Published, well-researched, well-scrutinized genealogies (such as Douglas, Pierce, Matthew Cushing, ), corroboration with primary sources preferred
Tier 5: Posted genealogies which cite any of the above sources
Posted genealogies/trees with no source citations, or that cite only other posted genealogies, including LDS IGI and AF information, Ancestry.com and Rootsweb and other like sites
Unsourced information can be used to start research that, once substantiated, can be added to my tree. Authors of posted information can be contacted for leads or sources that might lead to substantiated information added to the tree.
10) Respect living family wishes regarding public information, such as fathers of children born outside of a marriage, etc.
11) Don't stir up old family feuds!