Demi Lovato and Wilmer Valderrama Mourn the Loss of Their Dog, Spawn, With a Heartbreaking Message

Demi and Wilmer say goodbye to another pet this year.

Demi Lovato and Wilmer Valderrama are both torn up about the loss of their beloved dog Spawn.

The 35-year-old actor broke the news on Sunday, with an emotional Instagram post about his late Doberman Pinscher.

"Yesterday, I said goodbye to my handsome boy Spawn," the former That '70s Show star wrote. "This year has been quite a roller coaster... Lots of emotions and lots of thresholds crossed. This boy was there for it all... 8 years worth of memories and ups and downs. ... No matter what I'd be going through, he just knew and would rest his little head on my lap as if saying, 'Dad, it's never that bad'... I would immediately smile and say 'OK, OK, you're right.'"

PHOTOS: Stars and Their Adorable Pets

"He had this presence, I mean he was just so freaking handsome... B**ches loved him and lads wanted to be him," he joked. "He loved people and people LOVED him. He was the BEST and perfect dog... So polite, so welcoming and just good a GOOD boy."

"Spawn my boy, you completed our family. You were the alpha and my son. I saw you go from a little pup with your ears taped to the most beautiful Doberman I have ever seen... I love you so much and I am going to miss you so freaking much. Touching you and kissing you for the last time last night was so painful. I just kept thinking I hope he's feeling my touch and hearing me say he was my son and that I loved him."

"Thinking of how loving you were my handsome boy," he later added, sharing photos of the two of them together. "I miss you Spawn."

Demi -- who lost her own dog Buddy in July reportedly due to a coyote attack -- also Instagrammed a sweet photo of Spawn licking her face.

"Saying goodbye absolutely broke my heart and I felt as if I was saying farewell to a family member," the 23-year-old "Confident" singer posted on Sunday. "The only thing that brings me comfort in this situation is knowing that Buddy is probably really happy he now gets to play with his big brother in Heaven... We love you so much Spawn... We miss you so much and we will never ever EVER forget you. RIP baby boy."

In spite of their loss, Demi and Wilmer still have their adorable dog Batman -- who Demi got for her birthday in August -- to comfort them. Last week, Demi reflected on how Batman came into her life with a bittersweet Instagram post.

"And even though my heart aches for Buddy, God did give me another little angel in my life and I wouldn't have him if I hadn't lost Buddy," she reflected. "It just goes to show you that everything happens for a reason and if you stay strong God gives you more incredible miracles. So here's my youngest son. My little snuggle bug and my little superhero... Batman."

And obviously, Batman enjoyed his Christmas with the couple.

"Food coma for @demisbatman... Yep, he's done," Wilmer joked this past Friday about the newest addition to their pack.

WATCH: Demi Lovato Flaunts Her Swimsuit Bod, Makes Out With Wilmer Valderrama

ET caught up with Demi earlier this month at Billboard's 10th Annual Women in Music event in New York City, where she talked about rumors that her longtime beau will propose in 2016! Watch below: