LaTeX cmd Error: Command '\titlefont' already defined.

I want to change the fonts for the title and headings of my document (rendering .rmd to pdf using latex engine xelatex). When trying to render, I keep getting the error:

"compilation failed- error
LaTeX cmd Error: Command '\titlefont' already defined."

even though \titlefont is called only once. I checked the log file and \titlefont only appears once, which is where the log lists the above error. I tried commenting out all other commands to try and isolate the problem, nothing worked.

Below is my header

---
title: "My PDF"
date: "`r Sys.Date()`"
output:
  pdf_document:
    latex_engine: xelatex
    fig_caption: true
fontsize: 12pt
geometry: "left=1.5cm, right=1.5cm"
header-includes:
    # - \usepackage{hyperref}
    # - \usepackage{booktabs}
    # - \usepackage{graphicx}
    # - \usepackage{wrapfig}
    # - \usepackage{floatflt}
    # - \usepackage{geometry}
    # - \setlength{\parindent}{15pt}
    # - \setlength{\parskip}{8pt}
    - \usepackage{fontspec}
    # - \usepackage{titlesec}
    - \setmainfont{Georgia}
    - \newfontfamily\titlefont{Georgia}
    # - \newfontfamily\subtitlefont{Latin Modern Roman}
    # - \newfontfamily\headingfont{Latin Modern Roman}
    # - \newfontfamily\captionfont{Latin Modern Roman}
    # - \DeclareCaptionFont{captionfont}{\captionfont} 
    # - \captionsetup{font=captionfont}
---

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