I'll write what I remember below.

Characters:

MC- Short, and is an older brother to a larger younger brother from the same clan/family.
Is from the Ox/Bull Family/Clan.
Is secretly strong.
Has an interest in runes/details put into weapons, and armor to enhance them with increase abilities.
An skill called a Hymn which can buff teammates, but when MC uses it, it only causes pain.

Younger Brother- Is twice the size of his younger brother.
Is from the Ox/bull family/clan.
Becomes a berserker around chapters 2-3.
Not very smart, but is amazingly strong.
Do to becoming a Berserker in the wrong way, he is injured and go's into a coma.

Loli looking nun- Mischievous.
Believes herself to be the MC's boss when he go's to work at the church in order to be able to learn how to make runes.
Secretly sneaks onto the carriage that the MC gets on to go to a dangerous place for a cure for his comatose brother.

Dungeon/labyrinth guide- Member of the Snake clan/family.
Gives a runed knife to the MC.
Meets up with MC at a bar, so as to guide him to where he needs herb used for his little brother.

Alchemist girl (This was where I left off then couldn't find the manga again)-
Wears glasses, and a hooded robe.
Hates people who think alchemists are useless, since they make the potions that the fighters use.
Hears about MC being strong, so in a fit of clouded anger decided to play a prank on him with alchemy.

Plot:
People fight with strong animal abilities based on their respective household I believe.
The story follows the MC, as he carries out his daily life while trying to make a decent life for his brother and him.

What I remember happening:

Starts of with MC and his brother getting insulted by a clan with higher status, calling the MC a weakling.
Later the MC puts on a disguise then go's to an arena where the snobby clan is located.
The MC challenges the leader to a fight, more geared towards examining the runed gear the leader uses.
The MC wins the fight, which in turn lets him take the leaders strength as energy for himself.

MC go's to find a place to work that involves making runes on armor, weapons, and tools.

Later the younger brother is attacked by the leaders underlings, and when they start insulting the MC, the younger brother loses it thus becoming a Berserker.

MC stops the younger brother by letting out a bit of his real abilities.
Which causes the younger brother to become comatose.

After MC finds the herb for his brother, he falls deeper into the dungeon(?) in a more dangerous area with a water dragon.

MC finds a small amazingly cute monster, but when he lets his guard down it attacks him with just enough strength to be annoying.

The MC is put into a situation where he and the cute monster (I think it looked like a fluffball with feet?) have to work together.

The MC gets out alive, but severely injured and has to be bed ridden.

I tried to be as descriptive as possible but this was all I could remember.
I've been looking for around a year now with no results.
I even only made this account just now to look for it here.
Any help is appreciated.

Hagane no Renkinjutsushi or Vinland Saga, maybe? I only did some genre searching, since I've never read the manga myself.

Edit: Added another manga choice.

** Shoujo & Romance Manga Lover || Cleaner-Typesetter**
[img]http://i.imgur.com/5h6vq7w.gif[/img]

There's a Zodiac tag if you want to try searching for it yourself.

Otherwise, I don't think these are it, but I thought of, Urami Koi, Koi, Urami Koi. and Flow. Though parts of what you said reminded me vaguely of Immortal Regis/Cavalier of the Abyss.

Sorry these aren't it, but I thank you for trying to help.

@Suxinn
These 4 are not it either, and I don't think that the Zodiac is relevant in the manga?
Most of the ones stated so far take place in an era around 2000's I think?
The one I'm trying to find had a medieval kind of era I believe.

Besides, all the manga so far said had nothing to do with 2 human brothers except Fullmetal Alchemist.
But even that one was off, since the main characters I talked about are nowhere in it.

Thank you anyways for your help.
I'll just keep looking for another week, while I wait for more replies to this thread.
If I don't find anything, or nobody can give me a clue on finding it in this thread I'll just give up on it.