Fifi Geldof Memorializes Her 'Beautiful Baby Sister' Peaches Geldof

April 8, 2014 -- Peaches Geldof 's relatives are struggling to come to grips with their grief a day after the 25-year-old British journalist's mysterious death.

Geldof's sister Fifi Geldof memorialized her sibling on Instagram today.

"My beautiful baby sister... Gone but never forgotten. I love you, Peaches x," Geldof wrote.

Her sister's death is under investigation by British police. Geldof was pronounced dead by paramedics who were called to her London home, athough officials told The Associated Press that they do not consider her death suspicious.

Peaches Geldof Dies at 25

Geldof's father, singer-songwriter Bob Geldof, released a statement Monday saying that her family is "beyond pain."

"She was the wildest, funniest, cleverest, wittiest and the most bonkers of all of us," he said. "What a beautiful child. How is this possible that we will not see her again? How is that bearable? We loved her and will cherish her forever."

The former model, a married mother of two young sons, is being compared to her late mother, television presenter and writer Paula Yates, who died at age 41 in 2000.