It is not yet clear what triggered the killings.
The family said they opted to lay Muchemi to rest on December 28 to coincide with her birthday, which was on November 28.
According to the family, the couple never had fights and are still in shock at what could have transpired.
Muchemi's younger brother Moses Muchemi noted the couple was the model marriage that anyone would want to have.
The family now wants the investigations agencies in the US to conduct thorough investigations to establish what could have transpired leading to the murders so that they can have closure.
On November 28, Gary posted on his Facebook status wishing his wife a happy birthday.
"Happy birthday to my wife. The love of life," he posted.
The status has since attracted over 300 comments and 14 shares with most of those commenting expressing their disbelief and sorrow.
The late Njoki had just buried his father, Geoffrey Migwi Muchemi who once worked at the Kenya Metrological Department. He passed on while in Lakewood, Washington and was later buried at his farm in Kiamaina, Kirinyaga County.