The mother of one Northern Virginia baby and the parents of another have been charged in their children’s deaths, Prince William County police said Monday.

The two infants, 4-month-old Jahari Jones and 9-month-old Avarice Alexander, died in 2014. But police and prosecutors did not decide to charge the adults with killing them until this year.

The charges in those two cases, which have not been previously reported, bring the number of homicide cases in Prince William in 2015 to 11, five more than in 2014.

The two babies are among the youngest victims of alleged homicide across the Washington region. Of the 287 homicides that The Washington Post has tracked in its database of killings in the area this year, authorities say six other victims are younger than 10 years old.

Jahari’s mother, Candice Christa Semidey, fed him and wrapped him in a blanket on Nov. 8, 2014, according to information provided by police spokesman Jonathan Perok on Monday in response to an inquiry by The Post. Then Semidey put Jahari down face first for a nap on a makeshift bed that she had fashioned from a chair cushion and a blanket, Perok said. She went to sleep, as well.

Unable to move and lying with his face toward the blanket, the baby suffocated. Semidey woke up and found she could not stir him. First-responders pronounced him dead at home, on the 16400 block of Kramer Estate Drive in Woodbridge.

Perok said Semidey, 25, did not mean to kill her child. But prosecutors concluded that the way she treated Jahari was so negligent as to be considered felony child neglect, and they charged her with felony murder — a charge for a death that occurs while a person is committing a felony, in this case the child neglect.

She was arrested Jan. 19. According to court records, she pleaded guilty to involuntary manslaughter and child neglect and was sentenced to a suspended prison term of five years, which she will not serve if she completes three years of probation.

Avarice died a month earlier, on Oct. 5, 2014. Police said her parents, Adam Jerell Vince Alexander and Jasmyne Alexandria Alexander, had put her in her crib the night before and had not checked on her for 16 hours.

The parents, both 21, had not taken Avarice to a doctor for seven months, even when they noticed she was having difficulty breathing four weeks before her death, investigators said. Instead, the parents first called for help when they found the girl unresponsive in her crib. She also was pronounced dead at home, on the 10200 block of Aqua View Court in Nokesville.

The Alexanders were charged with felony child neglect four days after their daughter’s death. In September, prosecutors indicted them on a count of manslaughter by negligence.

Court records show that Jasmyne Alexander was eventually tried on the less serious charge of child neglect and found not guilty this month. Adam Alexander is scheduled to go to trial on the charges of involuntary manslaughter and child neglect Jan. 26.