We cannot be the only things in this universe it is very big and there can even be more than one universe. Also it has been proven how big the universe is and also how many earth like planets there are. So we cannot be the only things in this universe so yes.
I know some people believe that heaven is not of the earth and is like a whole other realm and maybe that makes sense since humankind have witnessed so many different spiritual experiences whether them being good or evil but we see far less people who claim to have witnessed actual physical aliens and I think it is because there has not been any real alien sightings.
We do not have any proof that life does not exist on other planets. From plant life to other humans or life form, it is a possibility. Because we are not able to go to some planets for extended periods of time...we wouldn't really be able to say no. Therefore, I believe anything is possible.