As humans we are already dead in our sins and trespasses. You need to address that.
By the use of the word "brother" it indicates a fellow believer. If you see a fellow believer fall into drug use..that sin can physically kill them. It can be said to be a sin unto death. On the other hand we sin everyday...commit acts of unrighteousness that don't kill us.
Not talking about physical death but spiritual death
Jn 10:10
The thief cometh not, but for to steal, and to kill, and to destroy: I am come that they might have life, and that they might have it more abundantly.
Steal kill and destroy your soul!
1 Peter 5:8
Be sober, be vigilant; because your adversary the devil, as a roaring lion, walketh about, seeking whom he may devour:
Faithful
Rev 2:2 I know thy works, (not faith alone) and thy labour, and thy patience, and how thou canst not bear them which are evil: and thou hast tried them which say they are apostles, and are not, and hast found them liars:
3 And hast borne, and hast patience, and for my name's sake hast laboured, and hast not fainted.
4 Nevertheless I have somewhat against thee, because thou hast left thy first love.
5 Remember therefore from whence thou art fallen, and repent, and do the first works; or else I will come unto thee quickly, and will remove thy candlestick out of his place, except thou repent.
6 But this thou hast, that thou hatest the deeds of the Nicolaitanes, which I also hate.
7 He that hath an ear, let him hear what the Spirit saith unto the churches; To him that overcometh will I give to eat of the tree of life, which is in the midst of the paradise of God.
8 And unto the angel of the church in Smyrna write; These things saith the first and the last, which was dead, and is alive;
9 I know thy works, and tribulation, and poverty, (but thou art rich) and I know the blasphemy of them which say they are Jews, and are not, but are the synagogue of Satan.
10 Fear none of those things which thou shalt suffer: behold, the devil shall cast some of you into prison, that ye may be tried; and ye shall have tribulation ten days: be thou faithful unto death, and I will give thee a crown of life.
11 He that hath an ear, let him hear what the Spirit saith unto the churches; He that overcometh shall not be hurt of the second death.
Overcometh! Not He who has been saved by faith alone!
There is no beatitude that says: blessed are they who accept Christ by faith alone, they are justified and have salvation and cannot do anything to lose it!