Nick Carter has two more stops on his tour, but after that the singer plans on taking some time off to grieve following the death of his sister ... sources close to Carter tell TMZ.

According to our sources, Carter will play the last two tour dates (tonight in Chicago and tomorrow in Columbus) in memory of his sister Leslie, who passed away on January 31.

After that, we're told Nick will not schedule any more appearances ... and will take a couple of weeks to go off and deal with his sister's death. Our sources say Nick is still dealing with the fact that he missed her funeral.

As TMZ previously reported, the Carter family believes Leslie overdosed on prescription drugs.

Nick Carter tells TMZ ... he WANTED to attend his sister's funeral in NY this weekend, but his own family made it impossible for him to be there.

25-year-old Leslie Carter was laid to rest at a small ceremony in Upstate New York this weekend after a suspected prescription drug overdose. Several family members were present at the funeral, including Aaron Carter, but Nick was not.

Nick -- who was on the road performing at a concert at the time of the ceremony -- tells TMZ, “I wanted to be at my sister’s funeral, but my family has always had a complicated dynamic."

Nick would not get specific about the circumstances ... but sources close to the singer tell TMZ ... he feels family members went out of their way to make sure he was not included. 

Nick adds, "There are so many emotions for me surrounding the loss of my sister. I am trying to stay healthy, positive, and focused.” 


1:25 PM PT: We called Nick's sister Ginger Carter for comment -- she replied, "That's not true," and immediately hung up on us.

Leslie Carter was battling an addiction to prescription medication in the days before her death ... and family members believe she died as a result of an overdose.

Sources close to the "House of Carters" reality star tell TMZ ... the 25-year-old sister of Nick Carter had recently moved from Canada to Upstate New York to live with family members while she attempted to kick her addiction.

We're told family members had attempted to rid the home of any prescription medication -- including Xanax --  and were hopeful Leslie was on the road to recovery.

Sources say family members believed Leslie would be OK to stay alone in the home for roughly an hour yesterday while they ran errands ... but when they returned, Leslie was unconscious.

Officials were called to the scene ... but Leslie could not be saved.

We're told Leslie's 1-year-old daughter was not at home with Carter at the time of her death.

"House of Carters" reality star Leslie Carter -- younger sister of Backstreet Boys singer Nick Carter -- died yesterday in New York at the age of 25 ... the family confirms.

The Carters released a statement saying, "Our family is grieving right now and it’s a private matter. We are deeply saddened for the loss of our beloved sister, daughter, and granddaughter, Leslie Carter. We request the utmost privacy during this difficult time.”

The details surrounding Leslie's death are unclear.

Leslie was an aspiring singer, who gave birth to a daughter back in April.

Story developing ...