If you're using the free version of FamilyAlbum, it's not possible to hide third-party ads.
However, third-party ads are not shown in albums subscribed to Premium or Premium Pro.
https://family-album.com/premium
Note:
• When one member subscribes an album to a Premium plan (Premium of Premium Pro), all members of that album get access to Premium features.
• Non-third-party ads cannot be hidden, such as banners regarding FamilyAlbum products.