With the newest lass, can I claim my fiancé’s daughter (as well as my disabled sister) on my taxes?

I’ve heard conflicting opinions, so I was hoping someone here could help. My boyfriend & his daughter (8 years old) lived with for all of 2009. I supported them. He only worked about 1 month last year & asked me to claim his daughter. Her mother is not in her life (she has no rights to her, plus she was in jail the... show more I’ve heard conflicting opinions, so I was hoping someone here could help. My boyfriend & his daughter (8 years old) lived with for all of 2009. I supported them. He only worked about 1 month last year & asked me to claim his daughter. Her mother is not in her life (she has no rights to her, plus she was in jail the entire year of 2009). There is no one else that can claim her.
I’ve heard that due to new laws, that I could file “single” as claim my fiancé’s daughter as a “qualifying relative”, since she is blood related & not yet legally, related to me. I’ve been claiming my 48 year old sister (who is permanently & totally disabled) for several years now (she did not work at all last year & no one else can claim her). So could I file as “single” & claim them both as “qualifying relative”? If so, why does that work under “single” & not “head of household”?
Would this allow me to claim the “child tax credit” on my fiancé’s daughter & “Earned Income Credit” on both of them? Any other tips with this would be appreciated. Thank you!
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