Lola Sheen

Denise Richards is mourning the loss of Patrick Muldoon in a touching tribute to her ex and former "Starship Troopers" costar. The actress penned a lengthy letter on Instagram -- accompanied by a reel of pictures and video of them together -- Tuesday saying she was "deeply heartbroken" and…

Patrick Muldoon and Denise Richards broke up more than 25 years ago ... but he played a huge role in her family life -- so says her daughter Lola Sheen. Richards' middle child shared a throwback photo of the "Melrose Place" star standing alongside her mom ... writing, "the best duo there was" on…