This is probably the most important and frequently asked question I get asked by clients.
First, you need to understand that there is a sort of hierarchy in the universe and angelic realm. There is the first, second and third triads containing what religions and churches have established to follow some sort of an order.
The first triad contains Seraphim, Cherubim and Thrones angels. Seraphim angels are of pure light and include angels such as Michael, Metatron, Uriel, etc. Cherubim angels are the keepers of harmony, protection and wisdom. Angels such as Gabriel, Raphael and Zophiel are listed here. The Thrones angels are all about bringing justice and include Zaphkiel, Jolhiel, and Raziel to name a few.
The second triad contains the Dominions, Virtues, and Powers angels. In the Dominions set these are angels who keep track of the angel duties. Some examples include Zadkiel, Hashmal and Muriel. Next are the Virtues who are known as "miracle angels." Some examples of these angels include Gabriel, Michael, and Haniel. Michael and Gabriel have several important jobs as you can see, Lastly, the Powers angels keep track of human history and include Raphael, Camael, and Verchiel.
The third triad contains the Principalities, Archangels, and you guessed it Angels. Principalities protect politics and religion here on earth. Some examples are Naniel, Requel, and Amael. Archangels rule over all the angels. They love humans and one archangel can help multiple humans at one time. Pretty cool, huh? Some examples of these are Ariel, Gabriel (Again? Yup!), Metatron and Michael (Wow he's important). Lastly, we have our angels. They are messengers of God and their names are too many to list here. Just call out for whatever you need.
So, then why can't our loved ones be our guardian angels? There are only two angels/archangels who ever were humans first then became such. If you notice from the above listings, these lists are all angels who were only ever angels, not human. Unfortunately, we as humans have what is called "ego" and it gets in the way a lot. It's ok, just means that we have choice and make our own choices here on earth. Angels do not have such a thing. Your guardian angels were also gifted to you by God the moment you were born. Your family members you get to know them over time when you grow up. Some people are born into this world with one family and get placed in another. Your guardian angels have been there with you since day 1 regardless of what family you grew up with. Blood related or not. Therefore, your loved ones who pass can not be your guardian angels. But, they can ask for assistance from your angels when you need it and you call upon them to step in.
So remember, because loved ones were once on this earth making whatever choices they wanted to, they can not be your guardian angel. Angels have jobs and they stick to them and don't have an ego to get in the way of doing their jobs. They just want to help and be there when they are needed. Your loved ones can ask your angels to step in and do their jobs. But most likely, your angels are already "on it" so to speak.
Hope this cleared the air a bit! Ask your angels to step in as needed or just talk to them. That is what they are there for. Don't worry about a response. Most people don't get one, unless you are a medium! ;)